Our overarching goal is to improve patient safety in surgery for spinal stenosis. We hope to achieve this by better informing surgeons'and patients'treatment decisions with individualized data on operative risks. Spinal stenosis is narrowing of the spinal canal leading to compression of nerve roots. It is most common in older adults, resulting from degenerative changes in spinal structures. Stenosis surgery in adults over age 65 is the fastest-growing type of spine surgery in the U.S., with 40,000 operations/year and a national hospital bill to Medicare of $1.12 billion. However, risks are substantial in the older population and complication data are limited to small case series, so clinicians are often uncertain whether to recommend surgery and how extensive surgery should be. More comprehensive data will assist clinicians and patients in deciding whether to undertake this elective surgery and how extensive an operation can be safely performed. We propose to study complications and reoperations of lumbar stenosis surgery using Medicare claims and the VA's National Surgical Quality Improvement Program (NSQIP). Our aims are to (1) Determine rates and reasons for repeat spine surgery in the population and salient subgroups;(2) determine rates of life-threatening complications and 30-day mortality as a function of age, comorbidity, prior surgery, and surgical invasiveness;and (3) develop and validate prediction rules for major adverse events. Surgical invasiveness is a novel and important factor for study, as there is wide discretion in the number of spinal levels operated, use of a fusion procedure, anatomical approach, and the use of surgical implants. We hypothesize that these have an important impact on complication risk. Analyses will make use of our validated algorithm for identifying patients with lumbar surgery and our new index of surgical "invasiveness." These studies will enhance surgeons'ability to estimate operative risks and advise patients about the benefits and risks of spine surgery, thus improving patient safety in a high-risk context. Innovative aspects of the project are the use of a novel measure of elective procedural "invasiveness" as a risk factor in spine surgery;use of two population-based databases to increase robustness of the findings;and demonstration of new methods for monitoring the safety of surgical innovations, improving quality of care assessments, and individualizing informed consent documents. PUBLIC HEALTH RELEVANCE: A new method for estimating surgical risk will improve patient safety and assist in surgical decision-making, informed consent, monitoring surgical products, &improving quality assessment.